The present invention relates to gas pipe cables, and more particularly to a three phase gas pipe cable having three phase conductors arranged in an enclosing pipe and supported therein by supporting insulators.
In a conventional gas pipe cable, such as that disclosed in U.S. Pat. No. 3,919,456, three phase conductors are arranged within a common enclosing pipe. The phase conductors are arranged in a triangular configuration, and are each held on ring supports by supporting insulators. At each supporting location of each phase conductor two supports are provided. The longitundinal axes of the two supports intersect at an angle. Each axis is positioned with respect to the axes of the supports of the other phase conductors such that when the gas pipe cable is viewed in cross-section, the axis of each supporting insulator passes substantially through the centers of two phase conductors. In this simple and effective gas pipe arrangement, electrodynamic current forces occurring between the phase conductors, particularly in the case of a short circuit, may be controlled with little effort. However, such conventional gas pipe cables are subject to detrimental mechanical effects caused by differential heating of the phase conductors.
In conventional gas pipe cables the phase conductors are supported by supporting devices arranged periodically in the enclosing pipe. When the phase conductors are exposed to differential heating, the phase conductors undergo differential linear expansion. The differential linear expansion applies nonuniform shear stresses or torques to the supporting devices. Therefore, the supporting devices must be solidly anchored to the enclosing pipe using special methods which are cumbersome, labor intensive and costly. If such special methods are not employed, however, the differential linear expansion of the phase conductors may cause the supporting devices to overturn.
It is therefore an object of the present invention to provide a gas pipe cable in which the differential heating of the phase conductors, even in the case of short circuits, will not have detrimental mechanical effects on any part of the cable.